Nasty findings in places where cops let loose with tear gasTop News | Cindy Wan 12 Sep 2019
Tear gas residues can linger for weeks - 21 days in Sheung Wan, for instance - and pose health risks to residents, experts warned yesterday.
A team of 30 chemical engineers volunteered to test for residues in six districts that had seen protest action and police firing more than 2,000 tear gas canisters since June 12.
And they found residues on various surfaces weeks after the gas was used.
Michael Lee Ho-wun, who led the study, said the results were inconsistent with police claiming that residues would last for a short time.
Tear gasirritates the eyes, nose, mouth and lungs, causing symptoms such as crying, sneezing, coughing, breathing difficulties, eye pain and temporary blindness. It can also causechemical burns to exposed skin and set off allergies.
The engineers collected more than 200 samples in Sheung Wan, Sai Ying Pun, Admiralty, Sham Shui Po, Kowloon Bay and Tsuen Wan from August 18.
That involved the team using towels soaked with a solvent to collect dust from streets, walls of buildings, footbridges and around residential buildings. Laboratory tests then found residual amounts of two chemicals used to make tear gas.
A sample collected at the intersection of Des Voeux West Road and Sutherland Street showed residues 21 days after some 400 rounds of tear gas were fired in Sheung Wan clashes on July 28.
Places in Admiralty, Sai Ying Pun and Sham Shui Po were also found to have chemical residues two to three weeks after tear gas was used.
Lee noted that large quantities of tear gas were used in these areas, where the air flow is limited. Chemicals in narrow streets will stay longer due to poor ventilation, he said.
The team also found chemical residues under a bicycle footbridge in Tsuen Wan Park, which was 250 meters from a major confrontation zone on Yeung Uk Road. That was three days after tear gas was fired on August 25.
Lee said the affected area included a children's playground and the chemicals might have spread further. But his team could not expand the study.
He said he saw cleaners at work in Yeung Uk Road Wet Market without sufficient protection, meaning authorities were ignoring workers' health.
"I could feel my eyes tearing up in a toilet and in a lift to collect samples," he said. "But the cleaners were not wearing any protective gear." All they had were basic medical masks, he said.
The team found residues in flats at Telford Gardens in Kowloon Bay, near where tear gas was used on August 24. Residents were advised to clean furniture with soap and wet towels.
Lee urged police to use less tear gas and for authorities to test for residues in possibly contaminated areas.